The system and method enable simpler analog processing in a transmitter by reducing the number of bits in a digital signal through delta sigma modulation. Selection of current sources in a digital to analog converter of the transmitter is done using a randomization circuit.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A method, comprising: performing interpolation filtering on a digital quadrature signal, wherein the interpolation filtering reduces the digital quadrature signal from 12 bits to 10 bits; performing delta sigma modulation on the interpolated digital quadrature signal; coding the modulated signal with a thermometer code; converting the coded signal to an analog signal using randomly selected current sources of a Digital to Analog Converter; converting the analog signal to an RF signal; and transmitting the RF signal.
2. The method of claim 1 , wherein the modulation reduces the number of bits of the digital quadrature signal.
3. The method of claim 2 , wherein the reduction is from 10 bits to 4 bits.
4. The method of claim 1 , further comprising amplifying the RF signal before the transmitting.
5. The method of claim 1 , wherein the delta sigma modulation includes 2 nd order delta sigma modulation.
6. The method of claim 1 , wherein the digital quadrature signal is formed using one of GFSK, 4-PSK, and 8-PSK modulations.
7. A system, comprising: means for performing interpolation filtering on a digital quadrature signal, wherein the interpolation filtering reduces the digital quadrature signal from 12 bits to 10 bits; means for performing delta sigma modulation on the interpolated digital quadrature signal; means for coding the modulated signal with a thermometer code; means for converting the coded signal to an analog signal using randomly selected current sources of a Digital to Analog Converter; means for converting the analog signal to an RF signal; and means for transmitting the RF signal.
8. An RF transmitter, comprising: an interpolation filter configured to perform interpolation filtering on a digital quadrature signal, wherein the interpolation filtering reduces the digital quadrature signal from 12 bits to 10 bits; a delta sigma modulator configured to perform delta sigma modulation on the interpolated digital quadrature signal and configured to code the modulated signal with a thermometer code; a DAC, communicatively coupled to the delta sigma modulator, configured to convert the coded signal to an analog signal using randomly selected current sources; a mixer, communicatively coupled to the DAC, configured to convert the analog signal to an RF signal; and an antenna, communicatively coupled to the mixer, configured to transmit the RF signal.
9. The transmitter of claim 8 , wherein the modulation reduces the number of bits of the digital quadrature signal.
10. The transmitter of claim 9 , wherein the reduction is from 10 bits to 4 bits.
11. The transmitter of claim 8 , further comprising a power amplifier, communicatively coupled to the antenna and the mixer, capable of amplifying the RF signal before the antenna transmits the RF signal.
12. The transmitter of claim 8 , wherein the delta sigma modulator includes a 2nd order delta sigma modulator.
13. The transmitter of claim 8 , wherein the digital quadrature signal is formed using one of GFSK, 4-PSK, and 8-PSK modulations.
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June 29, 2004
October 20, 2009
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